package latest

import (
	"bytes"
	"context"
	"crypto/tls"
	"io"
	"net"
	"net/http"
	"net/http/httptest"
	"net/netip"
	"testing"
)

func TestCoverFetcherFetchesPublicHTTPSImage(t *testing.T) {
	server := httptest.NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.TLS == nil {
			t.Fatal("cover request was not made over TLS")
		}
		w.Header().Set("Content-Type", "image/jpeg")
		io.WriteString(w, "cover-bytes")
	}))
	defer server.Close()

	transport := server.Client().Transport.(*http.Transport).Clone()
	transport.TLSClientConfig = &tls.Config{InsecureSkipVerify: true} // test server certificate
	transport.DialContext = func(ctx context.Context, network, _ string) (net.Conn, error) {
		return (&net.Dialer{}).DialContext(ctx, network, server.Listener.Addr().String())
	}
	client := &http.Client{Transport: transport}
	fetcher := newCoverFetcher(client, func(context.Context, string) ([]netip.Addr, error) {
		return []netip.Addr{netip.MustParseAddr("198.51.100.10")}, nil
	})

	body, contentType, err := fetcher.Fetch(context.Background(), "https://cdn.example/cover.jpg")
	if err != nil {
		t.Fatalf("Fetch: %v", err)
	}
	if string(body) != "cover-bytes" || contentType != "image/jpeg" {
		t.Fatalf("Fetch = (%q, %q), want (cover-bytes, image/jpeg)", body, contentType)
	}
}

func TestNewCoverFetcherRechecksResolverBeforeConnection(t *testing.T) {
	var requests int
	server := httptest.NewTLSServer(http.HandlerFunc(func(http.ResponseWriter, *http.Request) {
		requests++
	}))
	defer server.Close()
	_, port, err := net.SplitHostPort(server.Listener.Addr().String())
	if err != nil {
		t.Fatalf("server address: %v", err)
	}

	resolves := 0
	fetcher := NewCoverFetcherWithResolver(func(context.Context, string) ([]netip.Addr, error) {
		resolves++
		if resolves == 1 {
			return []netip.Addr{netip.MustParseAddr("198.51.100.10")}, nil
		}
		return []netip.Addr{netip.MustParseAddr("127.0.0.1")}, nil
	})
	_, _, err = fetcher.Fetch(context.Background(), "https://cdn.example:"+port+"/cover.jpg")
	if err == nil {
		t.Fatal("Fetch accepted a destination that became private")
	}
	if resolves != 2 {
		t.Fatalf("resolver calls = %d, want preflight and dial checks", resolves)
	}
	if requests != 0 {
		t.Fatalf("requests = %d, want 0", requests)
	}
}

type roundTripFunc func(*http.Request) (*http.Response, error)

func (f roundTripFunc) RoundTrip(r *http.Request) (*http.Response, error) { return f(r) }

func coverResponse(status int, contentType, location string, body []byte) *http.Response {
	header := make(http.Header)
	if contentType != "" {
		header.Set("Content-Type", contentType)
	}
	if location != "" {
		header.Set("Location", location)
	}
	return &http.Response{
		StatusCode:    status,
		Status:        http.StatusText(status),
		Header:        header,
		Body:          io.NopCloser(bytes.NewReader(body)),
		ContentLength: int64(len(body)),
	}
}

func TestCoverFetcherRefusesUnsafeDestinationsBeforeRequest(t *testing.T) {
	var calls int
	client := &http.Client{Transport: roundTripFunc(func(*http.Request) (*http.Response, error) {
		calls++
		return coverResponse(http.StatusOK, "image/jpeg", "", []byte("must not reach network")), nil
	})}
	resolve := func(_ context.Context, host string) ([]netip.Addr, error) {
		switch host {
		case "loopback.example":
			return []netip.Addr{netip.MustParseAddr("127.0.0.1")}, nil
		case "private.example":
			return []netip.Addr{netip.MustParseAddr("10.0.0.1")}, nil
		case "linklocal.example":
			return []netip.Addr{netip.MustParseAddr("169.254.1.1")}, nil
		case "unique-local.example":
			return []netip.Addr{netip.MustParseAddr("fc00::1")}, nil
		case "cgnat.example":
			return []netip.Addr{netip.MustParseAddr("100.64.0.1")}, nil
		default:
			return []netip.Addr{netip.MustParseAddr("198.51.100.10")}, nil
		}
	}
	fetcher := newCoverFetcher(client, resolve)

	tests := []string{
		"http://public.example/cover.jpg",
		"https://127.0.0.1/cover.jpg",
		"https://10.0.0.1/cover.jpg",
		"https://169.254.1.1/cover.jpg",
		"https://[fc00::1]/cover.jpg",
		"https://100.64.0.1/cover.jpg",
		"https://loopback.example/cover.jpg",
		"https://private.example/cover.jpg",
		"https://linklocal.example/cover.jpg",
		"https://unique-local.example/cover.jpg",
		"https://cgnat.example/cover.jpg",
	}
	for _, sourceURL := range tests {
		t.Run(sourceURL, func(t *testing.T) {
			calls = 0
			if _, _, err := fetcher.Fetch(context.Background(), sourceURL); err == nil {
				t.Fatal("Fetch accepted refused destination")
			}
			if calls != 0 {
				t.Fatalf("network calls = %d, want 0", calls)
			}
		})
	}
}

func TestCoverFetcherStopsRedirectIntoPrivateAddress(t *testing.T) {
	var calls int
	client := &http.Client{Transport: roundTripFunc(func(req *http.Request) (*http.Response, error) {
		calls++
		if req.URL.Hostname() != "cdn.example" {
			t.Fatalf("redirect reached %s", req.URL)
		}
		return coverResponse(http.StatusFound, "", "https://internal.example/cover.jpg", nil), nil
	})}
	fetcher := newCoverFetcher(client, func(_ context.Context, host string) ([]netip.Addr, error) {
		if host == "internal.example" {
			return []netip.Addr{netip.MustParseAddr("192.168.1.1")}, nil
		}
		return []netip.Addr{netip.MustParseAddr("198.51.100.10")}, nil
	})

	if _, _, err := fetcher.Fetch(context.Background(), "https://cdn.example/cover.jpg"); err == nil {
		t.Fatal("Fetch followed redirect into private address")
	}
	if calls != 1 {
		t.Fatalf("network calls = %d, want only public first hop", calls)
	}
}

func TestCoverFetcherRejectsOversizedBody(t *testing.T) {
	var calls int
	client := &http.Client{Transport: roundTripFunc(func(*http.Request) (*http.Response, error) {
		calls++
		response := coverResponse(http.StatusOK, "image/webp", "", bytes.Repeat([]byte("x"), maxBodyBytes+1))
		response.ContentLength = -1
		return response, nil
	})}
	fetcher := newCoverFetcher(client, func(context.Context, string) ([]netip.Addr, error) {
		return []netip.Addr{netip.MustParseAddr("198.51.100.10")}, nil
	})

	if _, _, err := fetcher.Fetch(context.Background(), "https://cdn.example/large.webp"); err == nil {
		t.Fatal("Fetch accepted oversized body")
	}
	if calls != 1 {
		t.Fatalf("network calls = %d, want 1", calls)
	}
}

func TestCoverFetcherRejectsNonImage(t *testing.T) {
	var calls int
	client := &http.Client{Transport: roundTripFunc(func(*http.Request) (*http.Response, error) {
		calls++
		return coverResponse(http.StatusOK, "text/html", "", []byte("challenge")), nil
	})}
	fetcher := newCoverFetcher(client, func(context.Context, string) ([]netip.Addr, error) {
		return []netip.Addr{netip.MustParseAddr("198.51.100.10")}, nil
	})

	if _, _, err := fetcher.Fetch(context.Background(), "https://cdn.example/challenge"); err == nil {
		t.Fatal("Fetch accepted non-image response")
	}
	if calls != 1 {
		t.Fatalf("network calls = %d, want 1", calls)
	}
}